1. Field of the Invention
This invention relates to a prosthesis for use in a human heart as a valve and specifically to an artificial heart valve that reduces or eliminates stagnation and the possibility of thrombosis while increasing the available blood flow area through the valve without using hinges.
2. Description of Related Art
The use of artificial prostheses as substitutes for valves in the human heart is known in the prior art. The human heart has four one-way valves which, based on the hemostatic pressure on either side of the valve, allows blood to flow through the valve in one direction while preventing the flow of blood in the opposite direction. There is a valve between the right atrium and the right ventricle and a valve between the right ventricle and the pulmonary artery which goes to the lungs. There is a valve from the left atrium to the left ventricle and a valve between the left ventricle to the aorta. Although the use of artificial heart valves have been quite successful to replace defective human heart valves, there are some drawbacks that are of concern. Specifically, if the cross-sectional structure and configuration of the artificial valve, when open, is such that local areas of the valve structure itself impede blood flow through the valve opening, the result is blood flow stagnation at the same time the blood is being pumped through the valve opening. Stagnation is a term that means a lack of blood flow or blood movement caused by obstructions in the flow path. Such stagnation in the blood flow can possibly cause thrombosis, which is undesirable.
Another problem with many artificial heart valves is that the valve mechanisms typically include hinges which can become immobile through interaction with organic material in the blood stream and the surrounding blood vessels which can cause the valve mechanism itself to malfunction. A hinged heart valve usually includes one or two barrier plates that are connected by one or more hinges to an annular frame. The plates open or close based on hemostatic pressure on each side of the heart valve, pivoting about the hinge mechanism. If the hinge fails, the plates are stuck open, closed or partially open resulting in a dangerous medical problem. It is desirous to eliminate hinge problems in artificial heart valves.
U.S. Pat. No. 4,183,103 issued to Bloch, Jan. 15, 1980, shows a prosthetic one-way heart valve that uses a circular disc. The circular disc is supported in such a way that it occupies the center of the chamber thus blocking a significant amount of blood flow when the valve is open. U.S. Pat. No. 4,416,029 issued to Kaster, Nov. 22, 1983 shows a tri-leaflet prosthetic heart valve that uses three leaflets suspended on a plurality of arms which also act to increase the complexity of the device while at the same time blocking significant portions of blood flow through the valve opening. U.S. Pat. No. 4,494,253 issued to Bicer, Jan. 22, 1985 shows a cardiovascular valve prosthesis using a circular disc that is mounted in the open position near the center of the valve, blocking blood flow.
U.S. Pat. No. 4,532,659 shows a prosthetic heart valve with a plano-convex disc occluder. In the valve open position, the disc shaped surface occupies a center portion of flow through the valve. U.S. Pat. No. 4,655,772 shows a cardiac valvular prosthesis issued to Dr. Liotta et al, Apr. 7, 1987. This artificial heart valve shows a pair of leaflets which are hinged to permit movement of the leaflets from the closed to the open position. The hinge structure and action are undesirable and include hinge stops which protrude into the mainstream of the blood flow in an open position resulting in areas of potential stagnation and hinge problems because of the hinge structure. U.S. Pat. No. 4,713,071 issued Dec. 15, 1987 to Iofis, et al, shows a heart valve prosthesis with a disc that is slightly offset but that still occupies a large flow area near the center of flow thereby reducing flow.
U.S. Pat. No. 4,822,355 issued Apr. 18, 1989 shows a heart valve assembly that again has a disc mounted in the open position to occupy a central portion of the valve, blocking flow. U.S. Pat. No. 5,135,538 issued Aug. 4, 1992 to Pawlek, et al shows a disc shaped valve member that is slightly offset from the center of flow.
Thus the prior art shows artificial heart valves which by their construction and design impede blood flow when the valve is in an open position which can create stagnation leading to thrombosis and which include hinges in some instances that themselves can be subject to malfunction due to interaction with organic materials in the bloodstream and the vessel network.
The present invention overcomes the problems shown in the prior art.